Process of metallic cementation

ABSTRACT

CHROMIUM CEMENTATION PROCESS COMPRISES HEATING AN OBJECT TO BE CEMENTED ALONG WITH A POROUS BODY OF CHROMIUM WHICH HAS ABSORBED CHROMIUM HALIDE IN ORDER TO EFFECT A CHROMIUM CEMENTATION OF THE OBJECT. THE OBJECT TO BE CEMENTED MAY BE PLACED IN A CHAMBER ALONG WITH ONE OR MORE OF THE AGENTS AND BOTH HEATED TOGETHER IN THE CHAMBER WHICH MAY ADVANTAGEOUSLY BE AN ELECTRIC FURNACE CHAMBER. THE OBJECT TO BE CEMENTED WITH CHROMIUM MAY ALSO BE PLACED IN AN ELECTRIC FURNACE SEPARATELY AND THE PLACED IN A HALIDE GENERATING APPARATUS WHEREIN THE METAL HALIDE FINE PARTICLES ARE CARRIED BY AN UNOXIDIZING GAS INTO THE ELECTRIC FURNACE INTO CONTACT WITH THE OBJECT TO BE CEMENTED. A FURTHER ARRANGEMENT IS TO PLACE THE AGENT IN A TANK CONTAINING NEUTRAL SALTS WHICH IS CONTAINED IN THE FURNACE AND THEN HEATING THE AGENT ALONG WITH THE OBJECT TO BE CEMENTED WHICH IS   ALSO PLACED IN THE TANK. THE APPARATUS EMPLOYED MAY COMPRISE A SEPARATED FURNACE HAVING A HALIDE GENERATING APPARATUS CONNECTED THERETHROUGH TO A CONNECTING LINE AND WITH A FAN IN THE FURNACE FOR CIRCULATING THE GAS WHICH IS DIRECTED FIRST TO THE HALIDE GENERATING APPARATUS AND THEN THROUGH THE CONNECTING LINE INTO THE ELECTRIC FURNACE.

Dec. 11, 1973 N. KANETAKE ET AL 3,778,298

PROCESS OF METALLIC CEMENTATION Filed May 1971 United States Patent 3,778,298 PROCESS OF METALLIC CEMENTATION Norio Kanetake, Tokyo, and Hiroshi Shirai, Yokohama,

Japan, assignors to Kabushiki Kaisha Kito, Kawasakishi, Kanagawa-ken, Japan Filed May 3, 1971, Ser. No. 139,600 Int. Cl. C23c 11/04 US. Cl. 117107.2 R Claims ABSTRACT OF THE DISCLOSURE A chromium cementation process comprises heating an object to be cemented along with a porous body of chromium which has absorbed chromium halide in order to effect a chromium cementation of the object. The object to be cemented may be placed in a chamber along with one or more of the agents and both heated together in the chamber which may advantageously be an electric furnace chamber. The object to be cemented with chromium may also be placed in an electric furnace separately and the agent placed in a halide generating apparatus wherein the metal halide fine particles are carried by an unoxidizing gas into the electric furnace into contact with the object to be cemented. A further arrangement is to place the agent in a tank containing neutral salts which is contained in the furnace and then heating the agent along with the object to be cemented which is also placed in the tank. The apparatus employed may comprise a separate furnace having a halide generating apparatus connected therethrough to a connecting line and with a fan in the furnace for circulating the gas which is directed first to the halide generating apparatus and then through the connecting line into the electric furnace.

BACKGROUND OF THE INVENTION Field of the invention This invention relates in general to an apparatus and method for chromium cementation and in particular to a new and useful chromium cementation process in which the object to be cemented along with a porous body of chromium which has absorbed chromium halide is heated.

Description of the prior art Up to this time, a chromium cementing agent being used in case of cementing chromium in the steel product is hygroscopic and so it is liable to contain moisture while it is kept in custody until it is used for chromium cementation treatment after its manufacture or while it is being handled. When the chromium cementing agent containing moisture or hydroxyl like this is received and heated in a treatment chamber for chromium cementation, chromium oxide is produced and also in case a chromium cementation treatment is performed with a chromium cementing agent containing carbon, chromium carbide is produced by the heating of the agent in the treatment chamber and since this chromium oxide or chromium carbide is difficult to cement to a steel product or the like, there is a defect that cementation of chromium cannot sufficiently and efficiently be performed.

SUMMARY OF THE INVENTION This invention aims at providing a process of deeply 3,778,298 Patented Dec. 11, 1973 cementing agent which is non-hygroscopic and does not contain hydroxyl and carbon. The first invention relates to a process of chromium cementation characterized in that in the treatment chamber there are received the object to be cementation treated and the chromium cementing agent. The agent comprises a porous body of chromium which absorbs chromium halide and does not contain moisture, hydroxyl and carbon, and the air in the treatment chamber is expelled by non-oxidizing gas and then the inside of the treatment chamber is heated and thus a chromium cementation takes place. The second invention relates to a process of chromium cementation, characterized in that in a chromium halide generating apparatus there is heated a chromium cementing agent consisting of a porous body of chromium which absorbs chromium halide and does not contain moisture, hydroxyl and carbon, thereby producing fine powders of chromium halide which are led into and heated in the treatment chamber in which the object to be cementation treated is received, and a chromium cementation is performed.

The present invention will be further explained in detail by each embodiment shown in the accompanying drawings in which FIG. 1 is a perspective view of chromium cementing agent being used in case of embodying this invention;

FIG. 2 is an enlarged view showing the condition of distribution of chromium particles and chromium halide particles in the chromium cementing agent;

FIGS. 3 and 4 are rough longitudinal sectional side views showing the condition in which a chromium cementation treatment is performed by the embodiment of this invention; and

FIG. 5 is a longitudinal sectional side view showing the condition in which a metallic cementation is performed by the embodiment of this invention.

Further, a suitable component of the chromium cementing agent being used in case of embodying this invention is as follows:

Chromium halide, for instance, chro- And the chromium cementing agent consisting of the substance having this component is in the condition that particles 2 of chromium halide are absorbed in the small gaps among chromium particles 1 as shown in FIG. 2, namely, the particles 2 of chromium halide are covered by the chromium particle groups and do not make contact with air in the atmosphere and therefore chromium halide does not absorb moisture. Further the chromium cementing agent may be formed in the shape of a hollow cylinder as shown in FIG. 1 or in the shape of sphere or the other optional shape.

EMBODIMENT The following are descriptions of various embodiments Of the invention:

As shown in FIG. 3, in a heating furnace (electric furnace) 5, namely, in the treatment chamber, there are receivedan object (gear) to be cementation treated made of carbon steel of 118 (Japanese Industrial Standard) 3 of 3 times the object to be cementation treated in weight, consisting of a porous substance which absorbs chromium chloride (CrCl 42% and which contains iron 0.01%, aluminum oxide (A1 12% and chromium of remaining amount and which does not contain moisture, hydroxyl and carbon; a non-oxidizing gas, such as argon gas or nitrogen gas or the like, is supplied in the heating furnace 5 at room temperature and after the air in the heating furnace is expelled by that non-oxidizing gas, the inside of the heating furnace is heated and whereby the fine particles of chromium chloride (CrCl evaporate from the chromium cementing agent and float in the atmosphere within the heating furnace and the fine particles of that chromium chloride become a semi-fused condition on the surface or the whole of the furnace and thus chromium is cemented on the surface of the object to be cementation treated.

Next, after the temperature in the heating furnace is lowered to room temperature, the product on which chromium was cemented is taken out. When a temperature in said furnace is kept at 950 C. and treatment for 3 hours was made, a chromium cementation layer of 3 in thickness can be obtained on the surface of the object to be cementation treated and when a temperature in the furnace is kept at 950 C. and treatment for 15 hours was made, a chromium cementation layer of 35 1. can be obtained and the surfaces of those chromium cementation layers were all smooth and had a brightness.

Further, the chromium cementing agent can also be around 5 times the weight of the object to be treated.

EMBODIMENT 2 As shown in FIG. 4, a gas feed pipe 9 is connected to one end of a mufiie 7 in a chromium halide generating apparatus 8 comprising a heating furnace 6 and the mufile 7, and one end of a chromium halide feed pipe 11 having a valve 10 is connected to the other end of the muflie 7 and further the other end of that feed pipe 11 is connected to the heating furnace (electric furnace) 5 having a fan 12 and an exhaust valve 13 and an object 4 to be cementation treated of the same material as that in the case Of Embodiment 1 is received in the heating furnace 5 and a chromium cementing agent 3 (100 kg. in Weight) of the same substance as that in the case of Embodiment 1 is received in the muffle 7 and then the inside of the mufiie 7 is heated to the tempertaure of 1050 C. and the fine particles of chromium halide evaporate from the chromium cementing agent 3 a non-oxidizing gas (argon gas) is supplied from the gas feed pipe 9 and this non-oxidizing gas containing the fine particles of chromium chloride is supplied in the heating furnace 5 and a chromium cementation treatment for 5 hours takes place at a treatment temperature of 1000 C. The product obtained had a chromium cementation layer of 5 and a brightness on its surface.

Since this invention is constituted as previously mentioned, the fine particles of chromium halide in the chromium cementing agent are covered by the chromium fine particle groups and absorption of moisture by chromium halide can be prevented and that chromium cementing agent does not contain hydroxyl and carbon and the air in the treatment chamber for chromium cementation is substituted by inert gas beforehand and therefore even if the inside of the treatment chamber is heated, production of chromium oxide or chromium carbide can be prevented. Accordingly, a depth of chromium cementation can be made large and a chromium cementation can efiiciently be effected. And by leading the fine powders of chromium halide generated in the chromium halide generating apparatus beforehand into the treatment chamber, fine powders of chromium halide are quickly supplied and floated in the treatment chamber and in a chromium cementation treatment can be more efiiciently and continuously effected.

S2OC and a hollow cylindrical chromium cementing ag nt, 1 FIG. .5. shows the .second embodiment of. the condition in which a chromium cementation treatment embodying this invention takes place. First, a large number of cylindrical chromium cementing agents 24 are placed at the bottom of a treatment tank 23 which is received in an electric furnace 21 and which is supported by firebricks 22 and a steel product 26 to be treated is placed on a perforated support stand 25 provided in the treatment tank 23 and neutral salts 27 are received in the treatment tank 23 and the chromium cementing agent 24 and the steel product 26 to be treated are immersed in the neutral salts 27. 1

Next, a peripheral side plate 30 of a lid 29 'i inserted in a peripheral edge groove 28 provided at the upper part of the treatment tank 23 and sealing powders 31 areapplied between the peripheral edge groove 28 and theperipheral side plate 30. Inert gas, such as argon gas, or nitrogen gas is supplied from an air feed port 32 provided in the lid 29 and is exhausted from an exhaust port 33; and after the air in the treatment tank 23 is displaced by inert gas, the air feed port 32 and the exhaust port 33 are closed and heating for 2 hours is made at about 1000 C. by the electric furnace 21 and thus a chromium cementation in the steel product to be treated takes place.

The operation of the second embodiment is as follows:

In the treatment tank shown in the drawing, there are received neutral salts with a ratio of sodium chloride 40%, barium chloride 30% and potassium chloride 10%, and there is received 20% of a hollow cylindrical chromium cementing agent consisting of porous substance which absorbs chromium chloride 42% and which contains iron 0.01%, aluminium oxide 12% and chromium of the remaining amount and which does not contain moisture, hydroxyl and carbon, and in the neutral salts within said treatment tank there is immersed a gear with a chemical component of C: 0.21%, Si: 0.23%, Mn: 0.61%; P: 0.015%, S: 0.020%, and iron: remaining amount and treatment for 2 hours was effected at 1000 C. and as a result a chromium cementation layer of about 10;]. in thickness could be produced.

This invention is constituted as previously mentioned, namely, a metallic product to be treated is immersed in the neutral salts which are large in heat capacity and do not contain oxygen and heat treatment is effected and therefore oxidation is prevented and chromium cementation can take place and as the chromium cementing agent, particularly a porous body of chromium which absorbs chromium halide and which does not contain moisture, hydroxyl and carbon, is employed and therefore production of chromium oxide or chromium carbide can be prevented by the chromium cementing agent. Accordingly, a depth of chromium cementation can be made large and thus there is the effect that dechromium phenomenon can be prevented.

What we claim is:

1. A chromium cementation process for steel using a heating furnace for the object to be cemented, comprising placing the object to be cemented into the heating furnace, heating a cementing agent which comprises a porous body of chromium which has absorbed chromium halide to cause the chromium halide to evaporate and form gaseous chromium halide, directing an inert gas through the evaporated chromium halide gas to cool it and to form ffine particles of said chromium halide and to move the chromium halide particles along with the inert gas into association with the object to be cemented so that the fine particles of chromium halide form a semi-fused chromium halide coating on the object.

' 2. A chromium cementation process, according to claim 1, comprising adding a non-oxidizing gas such as argon to the vicinity of the agent and the object to be cemented.

3. A chromium cementation process, according to claim 1, wherein the agent is arranged in a chromium halide generating apparatus and the object to be cemented is arranged in a heating furnace and wherein the agent is heated in a chromium halide generating apparatus to generate fine powders of chromium halide which are led into said heating furnace.

4. A chromium cement'ation process, according to claim 1, wherein the agent comprises a hollow cylindrical chromium cementing agent approximately 3 times the weight of the object to be cemented and comprises a porous substance which absorbs chromium chloride in the amount of 42%, iron in the amount of 0.01%, aluminum oxide in the amount of 12%, and chromium the remaining amount.

5. A chromium cementation process, according to claim 4, using a halide generating apparatus wherein the temperature inside the halide generating apparatus is maintained at 1050 C. to cause the fine particles of chr0- mium halide to evaporate from the agent wherein the object in the heating furnace is subjected to a treatment temperature of 1000 C. for five hours.

References Cited UNITED STATES PATENTS 3,021,231 2/1962 Samuel et a1. 117-107.2 R X 3,066,044 11/1962 Samuel 117-107.2 R 2,874,070 2/1959 Galmiche 117107.2 R 2,955,957 10/1960 Dorner 117107.2 R 3,028,261 4/1962 Wachtell et a1. 117-107.2 R 3,375,128 3/1968 Baldi et a1 117107.2 R

FOREIGN PATENTS 617,849 2/1949 Great Britain 117107.2 R

RALPH S. KENDALL, Primary Examiner US. Cl. X.R. 

